ICB method of forming high refractive index films

Abstract

A uniform film of sapphire and tungsten is deposited onto a surface of a substrate using the ionized cluster beam ("ICB") apparatus. During ICB deposition, a tungsten crucible containing sapphire is heated until a vapor of sapphire and tungsten is formed. The tungsten crucible is heated to form a tungsten vapor, which causes the crucible material to mix with the sapphire, thereby forming a vapor mixture of sapphire and tungsten. The vapor is ejected through a small nozzle into a vacuum region. The resulting adiabatic expansion of the vapor promotes formation of atomic clusters. Some of the clusters are ionized, and electrons are stripped off the clusters. The clusters are accelerated toward the substrate, which is also within the vacuum region. The clusters impact the surface of the substrate, where they are deposited to form the uniform sapphire/tungsten film. The film is deposited in an sapphire (aluminum oxide)/tungsten ratio of 2:1. The film has a relatively high index of refraction of approximately 2.2, thereby rendering it useful as an optical coating (specifically, an electrochromic material). The film may also be used as a resistive or thermally conductive material.

Having thus described the invention, what is claimed is: 
     
       1. A method of forming a film comprised of sapphire and tungsten, the method comprising the steps of: providing a substrate having a surface;   providing sapphire material in a crucible comprised of tungsten material, the crucible having a nozzle;   heating the crucible to a predetermined temperature to cause a tungsten vapor to form, thereby causing the tungsten material to mix with the sapphire material within the crucible, the heating step also causing the mixture of sapphire material and tungsten material within the crucible to be vaporized at a predetermined vapor pressure, the crucible vapor pressure being greater in magnitude than a predetermined pressure value of a vacuum region external to the crucible, thereby causing the vapor to be ejected through the nozzle and into the vacuum region and forming clusters of atoms of the sapphire material and the tungsten material by adiabatic expansion, the atomic clusters being formed in the vacuum region outside of the crucible in the vicinity of the nozzle;   bombarding the atomic clusters with electrons, thereby resulting in at least one of the atomic clusters being partially ionized along with any remaining atomic clusters remaining non-ionized; and   accelerating both the ionized and non-ionized atomic clusters toward the surface of the substrate, thereby forming the film comprised of sapphire and tungsten on the surface of the substrate.   
     
     
       2. The method of claim 1, wherein the film is comprised of sapphire and tungsten in a sapphire to tungsten ratio of 2:1. 
     
     
       3. The method of claim 1, wherein the the film is deposited on the surface of the substrate at a rate of at least 100 Angstroms per minute. 
     
     
       4. A method of forming a film comprised of sapphire and tungsten, the method comprising the steps of: providing a substrate having a surface;   providing sapphire material and tungsten material in a mixture within a crucible, the crucible having a nozzle;   heating the crucible to a predetermined temperature to cause the sapphire material and tungsten material mixture within the crucible to be vaporized at a predetermined vapor pressure, the crucible vapor pressure being greater in magnitude than a predetermined pressure value of a vacuum region external to the crucible, thereby causing the vapor to be ejected through the nozzle and into the vacuum region and forming clusters of atoms of the sapphire material and the tungsten material by adiabatic expansion, the atomic clusters being formed in the vacuum region outside of the crucible in the vicinity of the nozzle;   bombarding the atomic clusters with electrons, thereby resulting in at least one of the atomic clusters being partially ionized along with any remaining atomic clusters remaining non-ionized; and   accelerating both the ionized and non-ionized atomic clusters toward the surface of the substrate, thereby forming the film comprised of sapphire and tungsten on the surface of the substrate.   
     
     
       5. The method of claim 4, wherein the film is comprised of sapphire and tungsten in a sapphire to tungsten ratio of 2:1. 
     
     
       6. The method of claim 4, wherein the the film is deposited on the surface of the substrate at a rate of at least 100 Angstroms per minute.